With input from Will Richardson, this blog software makes it easy to register students and does not require email addresses. It's called 21 Classes, and has already been reviewed by Steve Dembo on his blog Teach42.
Steve writes, "I do have to admit that this is probably the most well developed blog engine for educators." You may want start reading Teach42 which is a very active blog done by a fellow NICE member who has willingly shared his expertise.
Dembo commented that he is a New Trier Grad, class of '92.